FYS4250Fysisk institutt - Rikshospitalet. Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary.

FYS4250 Fysisk institutt - Rikshospitalet

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Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

”A sensor is a mediator able to convert one or more measurands or physical variables into an equivalent signal variable of another type of quantity within a frame of a given unity”

Pallàs-Areny, Webster, Sensors 2001

What is a sensor?



Image: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

- Sensor system: ”comprises the total signal path from the measurand to the observer and includes all sensing, conditioning and real-time processing elements in the path”

- Electrode: ” An electrode is an electrochemical cell converting charge carriers from ions to electrons or vice versa. An electrode is only a half-sensor in the way that two electrodes are necessary in order to apply a current or read a potential difference in living tissue”

- Probe: A ”probe is a broader concept than a sensor. A probe is often comprising multiparameter sensors (e.g. temperature) and may be held by the operator and be equipped with switches and level adjustment facilities. Example: Ultrasound probe”

Source: Grimnes-Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

More definitions....


Transducer - sensor (føler) - probe Position

Strain gages- Strain gages: ”are primarily displacement sensors based on variations

in the electrical resistance of conductors or semiconductors as a function of mechanical stress”



Image: www.conservationphysics.org

Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary Concepts.

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Pressure-transducer

Strain gauge:

R= L/A


Pressure-transducer

Strain gauge:

R= L/A

Pressure transducerand Wheatstone bridge

QuickTime™ and a decompressor


QuickTime™ and a decompressor




Force measurements


Force pressure

Semiconductor transducer Piezoresistive


Plethysmograph = volummåler


Inductive displacement sensors

L = n2Gμ


Linear VariableDifferential

Trafo (LVDT)

sign problem


Position detection, capacitive sensor


Piezoelectric

transducer

C=εA/x


Step response


2.ordersystem


Temperature measurements, termocouple

Thermocouple

Junction between metal A and B (hot junction), and an isothermal block with an ice bath temperature in connection to a voltmeter

A change in temperature will result in a voltage change readable on the voltmeter





Temperature measurement, termistor

]/)([0

00 TTTTt eRR −= β


Radiation thermometry

Black body radiation

Wiens law:λm=2898/T [μm]

Stefan-Boltzmann:Wt=εσT4 [W/cm2]


Radiation thermometer

Infrared ear thermometer



Image: Harsanyi, 2000, p 102


Fiberoptical thermometer, non-metallic


Optical instrument


Radiation sources


Light emitting diode (LED)


FiberopticsSnells lov: n2 sinθ2 = n1 sinθ1


Photomultipliers


Diode as a light detector

FYS4250Fysisk institutt - Rikshospitalet. Image: Grimnes, Høgetveit. Biomedical Engineering Education & Advanced Bioengineering Learning: Interdisciplinary.

Documents

la slide

termocouple slide

ax slide

volummler slide

g slide

order system slide

pressure transducer

interdisciplinary concepts